With the benefit of hindsight, we understand today that a three-paragraph statement issued by the Big Ten on Dec. 15, 2009, launched a period of conference realignment that reverberates today and will continue its profound impact on college sports for the foreseeable future.

The great shifts in college athletics can be traced to momentous events.

President Teddy Roosevelt’s sermon to representatives of Harvard, Yale and Princeton convinced early-20th Century football leaders to clean up the game’s dangerous tactics. The next year, in 1906, the forward pass was introduced and mass and gang tackling was banned. The game was saved.

In 1984, the Supreme Court ruled the NCAA could not determine the broadcast television fate of its schools, allowing schools and conference to test the free market and restructure conferences.

The most recent earth-shaking occasion, one that reverberates today and will continue its profound impact on college sports for the foreseeable future, made no grand entrance. It did not present itself as a declaration or ruling, and its effect could not have been projected on the day it happened — three years ago Saturday.

, issued by the Big Ten on Dec. 15, 2009, changed everything. The pivotal point begins at the second sentence of the second paragraph.

“The COP/C (Council of Presidents/Chancellors) believes that the timing is right for the conference to once again conduct a thorough evaluation for conference structure and expansion. As a result, the commissioner was asked to provide recommendations for consideration for the COP/C over the next 12 to 18 months.”

There it is. Not exactly a passage from the Magna Carta or Gettysburg Address, but the Big Ten’s desire to expand altered the college sports universe, and it continued to spin on Friday with the uncertainty of the Big East’s future.

The Big East’s seven schools that do not play major Division I football — four of them founding members in 1979 — reportedly have agreed to leave the conference, leaving the league in limbo over what remains, exit fees, the future of Madison Square Garden for the basketball tournament, even the Big East name.

It’s the latest drama that has been unceasing since the Big Ten’s statement was issued. The first move — Colorado from the Big 12 to the Pac-12 — didn’t happen for six months.

But there was plenty of realignment frenzy in the preceding months. Who was the Big Ten targeting? Notre Dame? Missouri? Nebraska? Rutgers, Syracuse, Pittsburgh and Connecticut, even Texas, all were floated.

Realignment started in earnest in June 2010 and hasn’t stopped.

New media deals were struck based on the new conditions. The Big 12 was on life support — twice — and now has revenue streams that once seemed impossible.

The Pac-12 didn’t get to 16 teams as commissioner Larry Scott desired, but is steady. The Atlantic Coast Conference — with Maryland pulled away by the Big Ten’s money and its other football-is-king schools looking desirable — is the most vulnerable after the Big East.

The 14-team Southeastern Conference reigns supreme at the sport that matters most, football, and hasn’t led any expansion expeditions after adding Missouri and Texas A

The Big Ten continues to do so, gobbling up land and markets for its Big Ten Network, when it appeared the waters had calmed, at least at the highest levels. There’s a sense — a fear among some conferences — that the league isn’t satisfied with 14 members, and may be issuing more statements before realignment is finished.